Capacitor charge sharing charge pump

Abstract

A multiphase charge pump including first and second phase charge pump circuits. Each of the first and second phase charge pump circuits includes a bootstrap capacitor. The bootstrap capacitors are switchingly connected by an equalization circuit that periodically transfers charge from a discharging capacitor to a charging capacitor, thereby reducing the charge that must be externally supplied to charge the charging capacitor.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a charge pump, and more particularly to a charge pump adapted to be included on an integrated circuit for converting a supplied voltage to a desired voltage. BACKGROUND OF THE INVENTION [0002] It is often useful to provide a voltage to a component on an integrated circuit chip that exceeds a voltage supplied to the chip. Elevated voltages are employed, for example, on DRAM integrated circuits for boosted wordline voltages and negative substrate bias voltages, and for writing and erasing EEPROMS. By generating requisite elevated voltages on the integrated circuit itself, the need for one or more external power supplies is eliminated. [0003] On an integrated circuit, inductors are more difficult to implement than capacitors. Thus, where various voltages are needed on an integrated circuit, it is advantageous to use a capacitive charge pump capable of transforming voltage without the use of inductors. [0004] Two important p...

AI Technical Summary

Benefits of technology

"The present invention is a multiphase charge pump that improves operating efficiency and reduces current requirements. It includes a first phase circuit with a first bootstrap capacitor and a second phase circuit with a second bootstrap capacitor. An equalization circuit is adapted to transfer charge between the two bootstrap capacitors based on a control signal. This results in a reduction of input current and waste current, and improves charge pump efficiency. The equalization circuit switches between the two driving sides prior to connection of the first and second capacitors, and the complementary operation occurs when the driving side of the second capacitor is at ground potential and the driving side of the first capacitor is at elevated potential."

Problems solved by technology

On an integrated circuit, inductors are more difficult to implement than capacitors.

This translates into a loss of 2-3 milliamps of supply current for every milliamp of pump output current.

As actually constructed, the single-phase charge pump circuit of FIG. 1 is relatively inefficient, and it produces an output voltage that varies significantly with time.

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